A technique making use of high biotin-avidin affinity (see, for example, “Methods Enzymol, 184, 5-(13, and 184, 14-(45) has been applied to immunoassays (for example, Japanese Patent Laid-Open Nos. Hei 4-363659 and Hei 6160387), biosensors (for example, Japanese Patent Laid-Open Nos. Hei 10-282040, Hei 9-292397 and Hei 8-94510), DNA operations (for example, Japanese Patent Laid-Open No. Hei 4-267896), separating materials (for example, Japanese Patent Laid-Open Nos. Hei 5-340945 and Hei 4-311397), and clinical therapies (for example, J. Nucl. Med. Commun., 12, 211–234(1991), and Int. J. cancer, 45, 1184–1189(1990)).
The above-described various methods need immobilization of biotin to a protein (glycoprotein), antibody, enzyme, chromophore, dextran or the like and for this purpose, various biotin immobilizing reagents have been put on the market (Methods Enzymol., 184, 123–138). These reagents serve to immobilize biotin to a biological material by reacting them with its reactive functional group such as amino group, sulfur group, carboxylic acid or alcohol (see, for example, “Molecular Probes Handbook of Fluorescent Probes and Research Chemicals, Chapter 4”) Biotin derivatives are employed for such an immobilizing reaction (see, for example, Molecular Probes Handbook of Fluorescent Probes and Research Chemicals, Chapter 4, p87). Immobilization of biotin to the terminal of polyethylene glycol by using these reagents has also been reported (Bioconjugate Chem., 8, 545–551(1997)).
The above-described immobilization of biotin is carried out based on the concept that biotin is immobilized by conducting one reaction with one functional group of an originally existing substance such as protein (see, for example, Japanese Patent Laid-Open No. Hei 6-148190).
Usefulness of biotin has thus been verified in various fields and there is a possibility of its industrial application leading to development of products exhibiting a new function. The above-described biotin immobilizing reagents are however expensive, which prevents industrial use thereof for immobilization of biotin. In addition, there is an eager demand for appearance of a heat sensitive polymer which aggregates in an aqueous solution or physiological saline by a cooling operation and exhibits an upper critical solution temperature (UCST), because its application to a separating agent or DDS is expected (Macromol. Chem., Rapid Commun., 13, 577–581(1992)).
The biotin immobilizing reagents immobilize biotin to a reactive functional group as described above so that protection of the functional group is sometimes necessary. Biotin immobilizing reaction itself is difficult in the case of immobilization to a functional group having large steric hindrance or immobilization of a biotin skeleton to a polymer chain. For example, when biotin is immobilized to a protein which is a macro molecule, deficiency of its functional groups prevents immobilization of a sufficient amount of biotin and in addition, biotin is immobilized only to the functional groups existing on the surface of the protein. The higher the polymerization degree of a polymer, the more difficult it becomes to immobilize biotin as desired by the conventional immobilizing method.
Accordingly, an object of the present invention is to synthesize or design a polyfunctional or multifunctional biotin-component-containing polymer applicable to various fields.
Another object of the invention is to industrially produce the biotin-component-containing polymer and to synthesize or design it in excellent economies and efficiency.
A further object of the present invention is to provide a heat sensitive polymer which aggregates in an aqueous solution by a cooling operation and exhibits an upper critical solution temperature (UCST) even in physiological saline; and a heat sensitive polymer which aggregates in an aqueous solution by a heating operation and has a lower critical solution temperature (LCST) in an aqueous solution.